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(No Model.) 4 Sheets-Sheet 1.

LLSH-BLEON. DIE PGR FURMING THREADS 0F SGRBWS.

Patented May 30, 1893.

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(Nq Model.) sheets-fsm 2.

. J, SHBLDON.

DIE FOR PORMING THREADS 0F SGREWS.

No. 498,582. Patented May, '30, 1893 b a z l co --a/ a xg? @y @d v o 'y 9.02 j

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' J. SHELDON.,

DIE POR PORMING THREADS OP SGREWS.4

Patented May 30, 1893.

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JOHN SHELDON, OF BIRMINGHAM, ENGLAND, ASSIGNOR TO THE NETTLE- A FOLD-S, LIMITED, OF SAME PLACE.

DIE FOR FORNIING THREADS OF SCRVEWS.

SPECIFICATION forming part of Letters Patent No. 498,582, dated May 30, 1893. Application le'd November l1, 1891. Serial No. 411,579. (No model.) Patented in England January 22, 1891, No. 1,193.

To a/ZZ whom it may concern.-

Be it known that I, JOHN SHELDON, of Birmingham,rEngland, a subject of the Queen of Great Britain, have invented a certain new and useful Improvement in Dies for Forming the Threads of Screws by Rolling, (for which I have obtained Letters Patent in Great Britain, No. 1,193, dated January 22, 1891;) and I do hereby declare that the following is a full, clear, and exact description of the invention, which will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to dies, whether flat or curved, for forming screw threads on screw blanks by rolling, and it consists'in` the novel construction of such dies as hereinafter described and claimed, reference being made to the accompanying drawings, in which- Figure 1, is a plan view of my improved die. Fig. 2 is a side elevation thereof. Fig. 3 is an elevation of the front end of said die. Fig. 4, is a similar view of the rear end. Fig. 5 is a section taken on the line rz-cc, Fig. 1. 6 comprises plan and end views, showing the peculiar lands and grooves enlarged. Fig. 7 is a sectional View showing a portion of the dies and screw blank when the said dies are in the position illustrated in Fig. 12. Fig. 8 is a similar view illustrating the parts when they are in the position shown in Fig. 13. Fig. 9 is a similar view when the parts are in the position shown in Fig. 14; Fig. 10, asimilar view when the parts are in the position shown in Fig. l5; Fig. 11, a similar view when the parts are in the position shown in Fig. 16. Figs. 12, 13, 14, 15, and .16, are detail views illustrating the manner of operation of.the dies upon the screw-blank.

In the said drawings, the reference letter a., indicates the working face of the die, h the grooves formed therein and c the lands between the grooves. The grooves b are formed by cutting knives or wheels or in any other suitable manner and are obliquely across the face of the die A. The lands c increase in diameter from their commencing to their finishing ends, and one side c of each land c, is uniformly inclined throughout its extent, and the other side h', of each land is formed with an inclination which gradually increases from the commencing to the finishing ends of said ing ends of thelands c. By the peculiar formation cf the lands c described, the screw thread formed by the dies isformed of metal gathered almost Wholly from one side of the troughs between the convolutions of the thread, and said screw thread is well developed in every part, that is from the commencement of the thread near the head to its termination on the taper point of the screw.

As shown in Figs. 3, 4 and 5, of the drawings a part of one side of the upper or working face of the die is inclined or raised, as at d, to operate upon the taper part of the screwblank, and the grooves in said inclined or raised portion are of less depth than those in that partof the die which operates upon the main portion of the screw blank, and the other part of the same side of the working face of the die is cut away as at c, in order that the die will not work upon the taper part of the screw-blank until the thread on the main part of the screw blankghas been partially formed.

In forming screw threads by means of the improved dies described, `two dies of like construction are employed, the screw blank being placed between said dies which are pressed with great force against the blank'while motion is given to the one relatively to the other. The screw thread is formed progressively, the lands of the diesin iirst'operating on the blank, penetrating to the depth or nearly to the depth of the trough between the threads of the tinished screw. There is thus formed a thread with a broad helical edge, as seen in Fig. 8. The subsequent action of the lands of the dies effects the expanding of the spaces between the partially formed thread, gradually fash-A ioning the displaced metal into the finished screw thread shown in Fig. 1 1 of the drawings. The screw thread made by the dies is formed of metal gathered almost wholly from one side of the troughs between the screw threads by the sides b of the lands c, the sides c of said lands having for their function only the smoothing'or finishing of the thread formed by the side b of the lands.

IOO

I am aware that heretofore dies for forming threads on screw blanks, have been constructed with lands which increase in diameter from their commencing to their finishing ends, but such lands are formed with sides both of which throughout their extent have a uniform inclination from bottom to top. The screw thread made by such dies is formed of metal gathered equally from both sides of the troughs or depressions between the convolutions of the thread, and such screw thread is found to be defective in that that portion of the screwthread nearest the head of the screw is not well developed and is not brought up to a sharp edge.

Dies constructed according to my invention differ from all prior dies, in that the lands arev formed With one side which has throughout its extent a uniform inclination and the other side of which is formed with an inclination which gradually increases from the commencing to the finishing ends of said lands.

The screw thread made by my improved dies is formed of metal gathered almost wholly from one side of the troughs between the con- Volutions of the thread, and is well developed in every part. v

Having thus described my invention, what I claim' is- A die for forming threads on screws, provided with lands, each of which lands increases in diameter from its commencing to its finishing end, one side of each of said lands having throughout its length a uniform degree of inclination and the other side of each of said lands formed with an inclination which gradually increases from the commencing to the inishing ends of said lands, substantially as described. e

JOHN SHELDON. [L S.] 

